Currently, every radio service (also referred to as radio layer) requires dedicated hardware in the form of special mobile communication modems. By means of a radio modem and in the manner described, one can generate a radio signal from digital transmit data (by modulation when transmitting), and receive digital data from a radio signal (by demodulation when receiving). For the communication or the exchange of communications data between motor vehicles amongst each other (Car2Car, see also https://www.car-2-car.org) or between a motor vehicle and an infrastructure component, such as a traffic light or a traffic sign (Car2I), there are currently two possible radio standards, of which one is based on a mobile communications standard, Long-Term Evolution (LTE), and the other is based on the wireless local area network (WLAN) standard. The described communication services are also grouped together as Car2X or vehicular ad hoc networks.
To provide the described Car2X communication universally in a motor vehicle, elaborate hardware is thus required that can operate both communications standards, in other words that can generate and receive the necessary radio frequencies, and can provide the associated protocol stack for communication control purposes. A protocol stack is hereby at least a program module, by means of which the communications data is processed, to hereby define a communications link between the motor vehicle on the one hand and an object in the vicinity on the other. For example, a protocol stack can implement the layers of the International Organization for Standardization Open System Interconnection (ISO-OSI) reference model.
A motor vehicle, which provides two communications standards, is known from EP 2 816 851 A1. According to it, two transceivers of different Radio Access Technology (RAT) are provided, which receive transmit data via a communications bus and generate from it a radio signal by modulation, or conversely generate receive data from a received radio signal by demodulation and can transmit it to the communications bus. Also connected to the communications bus is a digital signal processor, which generates the transmit data or processes the receive data. A disadvantage of this motor vehicle is that the conversion of transmit data into the radio signal or the conversion of the radio signal into receive data must be carried out by a separate mixer, which couples the bus to the transceivers. This requires an additional component and thereby makes the manufacture of the motor vehicle undesirably component-intensive.
A motor vehicle with a multi-Radio Access Technology (multi-RAT) system is known from US 2010/0234071 A1. Multiple protocol stacks can be provided by a processor. To transmit and receive radio signals, multiple high-frequency circuits are provided, which each have a mixer. This also makes manufacturing the system hardware-intensive.
From DE 10 2013 222 915 A1, a motor vehicle is known, in which two radio modems are provided, which can share one antenna. Providing two radio modems is also component-intensive.
From US 2003/0139179 A1, a communications system is known, which is equipped with two different network protocols. Two separate hardware radio interfaces are provided for this purpose.
From US 2007/0019672 A1, a communications system is known, which can switch between the Bluetooth™ standard and the ZigBee™ standard, wherein baseband modules are provided for these two communications standards, in other words hardware circuits, for this purpose. The protocol stacks are also partially implemented by the respective module.
From US 2009/0232191 A1, a communications system is known, in which a digital communications signal is converted by means of a digital mixer into a digital HF signal, which is converted by means of a digital analog converter into an analog HF signal.